Each causal model \(\mathcal {M}\)  is associated with a causal graph \(\mathcal {G}=\langle \mathbf {V},\mathbf {E} \rangle \) , where \(\mathbf {V}\)  is a set of nodes and \(\mathbf {E}\)  is a set of directed edges.
Each node in \(\mathcal {G}\)  corresponds to a variable \(V\)  in \(\mathcal {M}\) . Each edge, denoted by an arrow \(\rightarrow \) , points from each member of \(Pa(V)\)  toward \(V\)  to represent the direct causal relationship specified by equation \(f_{V}(\cdot )\) .
The well-known d-separation criterion [1]} connects the causal graph with conditional independence.
